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I’ve seen this issue a few times over the past months & most recently this past week with a customer. Luckily there’s a fairly simple fix to the issue published by Microsoft, but realizing not everyone remembers every Microsoft KB that gets released I thought I’d shine a spotlight on this one.

Scenario

As part of the migration process, when customers move their namespace from either Exchange 2007 or 2010 to 2013, HTTP connections start proxying through 2013 to the legacy Exchange Servers and some users will experience failures. The potential affected workloads are:
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Exchange Web Services (Free/Busy)
ActiveSync
OWA
Outlook

Test or new mailboxes may not be affected.

Resolution

The cause of this is the age old problem of Token Bloat. Users being members of too many groups or having large tokens.

The interesting thing in this scenario is that the issue was not experienced in the legacy version of Exchange & even if you look at the tokens themselves, they may not seem overly large. It seems that the process of proxying Exchange traffic is much more sensitive to this issue. Also, in a recent case that went to Microsoft, even if you increase the recommended values to a value higher than your current headers it may not have the desired effect. In our case we had to set the MaxRequestBytes & MaxFieldLength values to exactly match the values in the Microsoft KB (65536 (Decimal)).

Tools

I’m happy to announce a significant update to our scalability guidance for Exchange 2016. Effective immediately, we are increasing our maximum recommended memory for deployments of Exchange 2016 from 96 GB to 192 GB. This change is now reflected within our Exchange 2016 Sizing Guidance, as well as the latest release of the Exchange Server...

Over the last few months, we ran a TAP Program where our customers tested the batch migration process to move their public folders (both online and on-premises) to Office 365 Groups. We want to thank all of the customers who helped us out with the testing by sharing their experiences with us. The TAP program...